It may shock you, but modern cars are fairly more complicated than your 1939 plymouth.
Indeed they are. And some of those complications are genuine improvements. Let me list some of those.
1. Seat Belts (Although even in 1939 the Plymouth could have had seat belts had anyone thought to put them in cars)
2. Modern electronic ignition which truly is a substantial advance over carburetors (not that there were ever more than a dozen entities in the known universe who actually understood carburetors)
3. Materials. Just about everything on the cars -- tires, paint, brakes, working fluids, etc, etc, etc is better now. More durable, does its job better. Much is it a lot better.
4. Automatic transmissions -- I don't much care having, of necessity, mastered using a clutch in my youth. But a huge boon to those learning to drive
5. Anti-lock brakes. They work well on dry or wet roads which is where most people drive. And they work after a fashion on unpaved roads. They do not work worth a damn in snow and ice and actually make it harder to stop where one wants to stop pointed in the direction one wants to be pointed on icy roads.
6. Emission controls. Something of a PITA for most of us, but a real benefit to residents of some urban areas -- notably the Los Angeles basin.
7. Rear view cameras
OTOH not every improvement is actually an improvement or works all that well.
Case to point. Something called Electronic Stability Control. It's principle function seems to be to prevent the ascension of hills in Winter although I believe that it will also tell me if the car is upside down -- something many, I think most, drivers can likely figure out without help. It's complicated, adds expense and really looks to be kind of dumb. My mechanic agrees with me for what that's worth.
I'd also point out that it took a long time to get some of those things -- electronic ignitions, emission controls, automatic transmissions working right. Many decades in some cases.
My point -- not every idea is a good one. And doing stuff just because you can usually is not a very good idea. Cars nowadays often last 20 years or more. People need to be able to fix them. I don't think you need, or should want, complex electronics to replace something that is simple, straightforward, and works well -- headlights. OTOH the stuff on the back of the car -- taillights, licence plate lights, blinkers, backup lights, brake lights, rear view camera, proximity sensors -- is sufficiently diverse that installing a simple digital device and control via the CAN bus may be reasonable.